Switchgear configurations have current limits based on the heat rise over ambient room temperature. It is generally desired to limit the maximum temperature of the hottest spot on the switchgear main bus to 105° C. (a rise of 65° C. over an assumed ambient temperature of 40° C.), as directed by the standard IEEE 37.20.2. Typical medium and high-voltage metal-clad switchgear arrangements have maximum continuous current ratings of about 3000 A, due to heat generation. It is desirable to increase this current rating to about 4000 A.
A heat pipe can be attached in a retrofitted manner to the primary contact, which is the major hotspot in the actual switchgear assembly and the additional heat can be removed from the primary contacts by means of an evaporative cooling system having a condenser. While the contacts are cooled very efficiently, other parts more remote from the heat pipe (e.g., busbar joints) tended to overheat and need additional cooling enhancement (e.g., finned surface, heat spreader). Furthermore, the space inside of the switchgear compartments is very tight and optimized for the busbar electric clearance distance. The retrofitted heat pipe system needs to match this boundary condition. The tubing reaching from the primary contact to the condenser sitting on top of the switchgear enclosure is disposed beside the electrical supply system. In particular an insulated tubing section is constrained by the narrow space behind the primary contacts.
Thus, there is a need to provide a cooling apparatus for a switchgear that not only cools the primary contacts but also cools the busbars, without interfering with the electrical safety of the switchgear.